Parallel worlds are other universes that are similar or different from our universe, which may exist in different spatial dimensions or may be subtly related to our universe. Many physicists and astronomers believe that parallel worlds are not just imaginary in science fiction or TV series, but concepts that can be explored and verified in real science.
Columbia University physicist Brian Greene in his book Hidden Reality: Parallel Universes and the Laws of Deep Physics suggests a variety of possible types of parallel worlds, and discusses these surprising prospects in a PBS interview, The Mystery of the Universe. He believes that the universe we live in is just one of countless universes, and at least one parallel world is very close to us, perhaps only a millimeter away. But we cannot perceive the world because it exists in a spatial dimension different from our everyday reality.
Similarly, MIT physicist Max Tegmark believes that this "multiverse" model has a solid physical basis and can eventually be tested, predicted and falsified. "It's not science fiction, it's real science," he said. ”
So, how do you test and explore parallel worlds? Currently, scientists are using a variety of advanced equipment and methods to look for clues and evidence that parallel worlds may leave behind.
The first is the European Organization for Nuclear Research (CERN), located 100 meters underground near Geneva, Switzerland, which operates one of the largest, most powerful, most complex, most expensive, coldest, hottest, most empty, densest and most energy-dense machines – the Large Hadron Collider (LHC). The machine can accelerate two beams of protons to nearly the speed of light and collide with each other at four detectors. By analyzing the microscopic particles produced by the collision, scientists hope to discover some new physical phenomena, such as the existence of parallel worlds.
Why can the LHC detect parallel worlds? That's because if parallel worlds do exist, then they could affect gravity in our universe. According to Einstein's general theory of relativity, gravity can be understood as the curvature of space-time. If space-time has more than the four dimensions we know (three spatial and one temporal), then gravity has the potential to flow from our universe into additional dimensions. In this way, the energy required to create a black hole is reduced, because black holes are formed by extremely curved space-time. The LHC is the machine that can provide enough energy to produce mini black holes.
Miniature black holes are black holes with very small mass, small radius, short lifetime, and strong radiation. If the LHC can detect miniature black holes at specific energy levels, it means that there are additional dimensions that support string theory and related models that predict the existence of additional dimensions and parallel worlds.
So far, however, the LHC has not detected miniature black holes. This seems to indicate that there are no extra dimensions, at least not at the energy levels that have already been tested. However, some physicists have come up with a different explanation, arguing that the gravitational model used to predict the energy required to produce a black hole is not entirely accurate because it does not take quantum effects into account.
These physicists have come up with a new theory of gravity called gravity's rainbow. This theory is based on the assumption that light of different energies travels at different speeds in curved spacetime. This means that high-energy light and low-energy light see different space-time structures, just as different colors of light in a rainbow are refracted at different angles. Thus, in the "gravitational rainbow" theory, the gravitational constant G is not a constant, but an energy-dependent function. In this way, the critical energy required to produce a black hole also changes with energy.
According to the "gravitational rainbow" theory, the LHC could detect miniature black holes at 5.3 TeV or 9.5 TeV. If miniature black holes are indeed discovered, then it proves the validity of the "gravitational rainbow" theory and the extra dimension. The extra dimension further hints at the existence of parallel worlds.
In addition to the LHC, there are other devices and methods that can be used to find parallel worlds. For example, there is NASA's Wilkinson Microwave Anisotropy Explorer (WMAP), an artificial satellite launched in 2001 that measures the cosmic microwave background radiation (CMBR), the oldest light left after the Big Bang. By analyzing the temperature and polarization distribution of CMBRs, WMAP can reveal the age, composition, geometry, and evolutionary history of the universe.
Among them, the geometry of the universe is important for judging the existence of parallel worlds. If the universe is flat, then it means that there are no extra dimensions or parallel worlds. If the universe is curved, then there may be extra dimensions or parallel worlds. WMAP can tell if the universe is flat by looking at the brightest temperature fluctuations (or "spots") in the CMBR. If the universe were flat, then these spots would be about one degree in size; If not, then the spots will become larger or smaller.
According to WMAP's data analysis, the most likely outcome is that the observable universe we live in is flat. This means that Euclidean geometry as we know it still applies at the macroscopic scale, without extra dimensions or parallel worlds.
However, this does not exclude the existence of other forms of parallel worlds. For example, if we think of the observable universe as a giant bubble, then there may be other bubbles in larger space, forming a multiverse. These bubbles may have different laws of physics and history, or they may collide or split with ours. This multiverse model is called "eternal inflation" because inside each bubble, the expansion stops and forms a stable universe; Between bubbles, expansion continues and creates new bubbles.
To detect this parallel world, we need to look for some special signals, such as the possible "cold spot" in the CMBR, that is, the area of unusually low temperature, which may be caused by our bubble colliding with another bubble. If this hypothesis can be confirmed, it can provide direct evidence for parallel worlds.
In short, parallel worlds are a fascinating concept that challenges our perception of reality and possibility. While there is no conclusive evidence that parallel worlds actually exist, the possibility of their existence has not been ruled out. With the development of science and technology and the expansion of the scope of exploration, we may one day be able to unravel the mystery of parallel worlds and learn more about the universe in which we live.
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